jQuery UI DatePicker - Disable Days.

HTML

<script src="http://code.jquery.com/ui/1.10.3/jquery-ui.min.js"></script>
<link rel="stylesheet" href="http://code.jquery.com/ui/1.10.3/themes/redmond/jquery-ui.min.css">
<input type="text" class="datePicker" value="" />

CSS

.ui-datepicker-week-end a {
    color: red !important;
}

JavaScript

var unavailableDates = ["16-7-2018","17-7-2018","18-7-2018"];

function unavailable(date) {
  dmy = date.getDate() + "-" + (date.getMonth()+1) + "-" + date.getFullYear();
  if ($.inArray(dmy, unavailableDates) < 0) {
    return [true,"","Book Now"];
  } else {
    return [false,"","Booked Out"];
  }
}

$('.datePicker').datepicker({ beforeShowDay: unavailable });